Eijkman thought his germ theory was confirmed when he noticed the chickens in the hospital yard, which were fed on leftovers （剩饭） from the patients' plates, were also showing signs of the disease. He then tried to isolate the germ, but his experiments were interrupted by a hospital official, who declared that the polished rice, even though left over by the patients, was too good for chickens. It should be recooked for the patients, and the chickens should be fed on cheap rice with the outer layer still on the grain.
Eijkman noticed that the chickens began to recover on the new diet. He began to consider the possibility that eating unpolished rice somehow prevented or cured beri-beri —— even that a lack of some element in the husk might be the cause of the disease. Indeed this was the case. The element needed to prevent beri-beri was shortly afterwards isolated from rice husks and is now known as vitamin B. Nowadays, this terrible disease is much less common thanks to our knowledge of vitamins.
6. A good mixed diet ．
A. normally contains enough vitamins
B. still needs special provision of vitamins
C. is suitable for losing weight
D. is composed of fruits and vegetables
7. The disease beri-beri ．
A. kills large numbers of Eastern peoples
B. is a vitamin deficiency （缺乏） disease
C. is caused by diseased deer
D. can be caught from diseased chickens
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